Method of manufacturing steel tape



Patented Mar. 9, 1937 UNITED STATES PATENT OFFICE Albert T. Potter, Detroit, Mich., a-ssignor to Ainsworth Manufacturing Corporation, a corporation of Michigan Application November 26, 1934, Serial No. 754,741

2 Claims.

The invention relates to the manufacture of steel tapes which are transversely bowed in character.

In my co-pending application for patent, Serial No. 697,381, filed November 10, 1933, a windshield operating mechanism is disclosed and claimed, and this mechanism includes a transversely bowed, steel tape which is employed as an operating element for thrusting the windshield open. Accordingly, the tape must possess linear rigidity sumcient for thrusting the shield into its open position and holding it in this position. In this mechanism the tape is guided or bent partially around a sprocket wheel, and that portion of the tape moving around the sprocket wheel temporarily is flattened. It becomes apparent then that the tape not only must possess the desired linear rigidity, but it must be capable of passing through a bent and flattened condition and then returning to its bowed and straight condition, and withstanding these changes without noticeably impairing the ability of the tape to revert to its bowed condition, or without impairing its linear rigidity. The present invention is concerned principally with the manufacture of a tape of transversely bowed character, which may be efliciently and continuously used in the mechanism, and which will maintain its strength and its shape reverting characteristics.

The object of the invention therefore is to provide a method of manufacturing a tape of transversely bowed character, which will insure that the tape will constantly revert to its bowed condition without impairing its eificiency or its linear 35 rigidity.

For a better understanding of the invention, reference may be had to the accompanying drawing illustrating the method employed in manufacturing the tape, wherein:

40 Figure 1 is an elevational view illustrating a section of steel tape which is transversely bowed,

Fig. 2 is a side elevational view of the construction shown by Fig. 1.

Fig. 3 is a cross-sectional view taken substantially along the line 3-3 of Fig. 2

Fig. 4 is a side elevational view of mechanism employed in providing a transverse bow in a flat strip 015 the steel employed in making the tape.

Fig. 5 is a cross-sectional view taken substantially along the line 5-5 of Fig. 4.

Fig. 6 is a cross-sectional view taken substantially along the line 6-6 of Fig. 4.

Fig. 7 is a cross-sectional view taken substanl. tially along the line of Fig. 4, and

Fig. 8 is a cross-sectional view taken substantially along the line 88 of Fig. 4.

The tape in its finished condition is indicated at [0 in Figs. 1, 2 and 3, although in using the tape in a windshield operating mechanism, such as disclosed in the previously identified co-pending application for patent, it is provided with longitudinally spaced openings along its centerline, which are adapted to co-operate with the teeth on a sprocket wheel employed in imparting linear movement to the tape. The steel employed may be the so-called stainless steel and initially is manufactured in the form of a flat strip as indicated at l l in Figure 4. The first step employed in manufacturing the bowed tape comprises passing the fiat stock between a pair of rollers 12 and i3, which, as shown by Figure 5, form a bow or transverse curvature in the tape, which is of smaller radius than the curvature in the finished construction as shown by Figure 3. The tape then passes between rollers l4 and I5, which, as shown by Figure 6, still further decrease the radius of the curvature, and practically reduces the transverse shape of the tape to a semicircular cross-sectlon. These steps in the manufacture actually pass the tape through a critical stage, which may be termed its elastic limit, that causes the tape to receive a permanent set in which it tends to always revert to the curved condition without any tendency to revert to its flattened condition. The curvature shown by Figure 6, however, is greater than desired in a tape employed in operating Windshields, and accordingly following this step, its curvature is reduced by passing it between a pair of rollers I6 and H, which reduces its curvature as shown by Figure 7, and then pasing the tape between a pair of rollers l8 and I9, which still further reduce the curvature, as shown by Figure 8. A greater number of sets of. rollers may be employed than shown by Figure 4, and the final set of rollers reduces the curvature to that desired in the finished construction. It seems in pasing the tape through the first two sets of rollers, that the tape is given a permanent set, and is bowed beyond its elastic limit, and that even though the shape be changed subsequently by passing it between the last two pair of rollers, it retains its permanent set even though its curvature is reversed towards its flattened condition. For ordinary purposes, it may not be necessary to bow the tape past its elastic limit, as explained, but in a tape used for thrusting a windshield open, where durability and constant efficiency are required, greater linear rigidity and a permanent set are required so that it will not have any tendency to revert itself to a flattened condition, even though subjected to considerable linear thrusting forces and sharp bending during the operation.

Although only one form of the invention has been illustrated and described in detail, it will be apparent to those skilled in the art that various modifications may be made without departing from the scope of the appended claims.

I claim:

1. The method of manufacturing a normally straight, elongated, transversely bowed steel tape having great linear column stifiness and which flattens in the region of bending when the strip is bent longitudinally out 01' its normally straight condition and when the bending forces are sumcient to overcome the column stiffness and which strongly reverts to its normally straight bowed condition when the bending forces are removed, which comprises passing a substantially flat and elongated strip of spring stock through spaced pairs of rollers in a direction longitudinally of the strip, wherein the pairs of rollers progressively bow the strip in a transverse direction, first to a bow of smaller radius of curvature than desired and past the elastic limdt of the strip, and then in a reversing manner to a bow of larger radius oi. curvature and 01 substantially the shape desired,

thereby to impart to the strip great linear column stifl'ness and the ability to revert to its bowed condition after bending it longitudinally, during which the bending portion of the strip flattens.

2. The method of manufacturing a normally straight, elongated, transversely bowed steel tape having great linear column stifiness and which flattens in the region of bending when the strip is bent longitudinally out of its normally straight condition and when the bending forces are sumcient to overcome the column stiffness and which strongly reverts to its normally straight, bowed condition when the bending forces are removed, which comprises passing a substantially flat and elongated strip of spring stock through forming elements in a direction longitudinally of the strip, wherein the forming elements progressively bow the strip in a transverse direction, first to a bow of smaller radius of curvature than desired and past the elastic limit of the strip, and then in a i reversing manner to a bow of larger radius of curvature and substantially the shape desired, thereby to impart to the strip great linear column stiffness and the ability to revert to its bowed condition after bending it longitudinally, during which the bending portion of the strip flattens.

ALBERT T. PO'I'IER. 

